Products: Metachrome UV-Conversion Coatings for Sensors

Many detectors including front-illuminated CCDs, photodiode linear arrays, and select CMOS devices lack quantum efficiency in the UV spectral region. Acton Optics provides thin coatings to the surface of these devices effectively, reliably and inexpensively achieving a dramatic increase in device sensitivity in the 120 to 430nm range.

Metachrome® is a composite phosphor coating that improves the sensitivity of CCDs in blue-visible and ultraviolet (UV) wavelengths. The application of a thin coating of Metachrome to the surface of a CCD effectively, reliably, and inexpensively achieves a dramatic increase in device sensitivity in the 120 to 430-nm range. Both front-illuminated and back-illuminated CCDs will achieve improved UV response using Metachrome coating.

Download the Tech Brief that discusses how these proprietary coatings extend detection dapabilities of silicon-based photonic sensors into the ultraviolet.

Metachrome emits light at approximately 540 to 580 nm when excited with light below 450 nm. The high conversion efficiency of Metachrome, combined with the high quantum efficiency of CCDs at the emission wavelength, make Metachrome an ideal UV "down converter" for silicon detectors. Above 460 nm, the thin layer of Metachrome becomes transparent and therefore has no detrimental effect on the quantum efficiency of a CCD in the visible and near-infrared.

The front-illuminated CCD has virtually no response below 350 nm and less than 5% quantum efficiency is typically observed at 400 nm (in the blue-visible range). With the Metachrome coating, this same CCD exhibits 10% quantum efficiency below 350 nm. Back-illuminated CCDs also benefit from Metachrome coating. Using the Metachrome coating, the quantum efficiency improves by more than a factor of 10 at 250 nm. Metachrome coating provides a superior alternative to the best broadband UV antireflection coatings on back-illuminated CCDs because performance in the red portion of the spectrum is less compromised.

Above: Typical Quantum Efficiency of CCDs Coated with Lumogen E.

Spatial Resolution of CCDs coated with Metachrome

We have performed measurements to determine the effects of Metachrome coatings on spatial resolution. The contrast-transfer functions for a coated and uncoated CCD with a 20-µm square pixel were compared and found to be identical.